Stephen d



(No Model.)

S. D. FIELD.

PRINTING TELEGRAPH. No. 338,843. Patented Mar. 23, 1886.

UNTTED STATES PATENT OFFICE.

STEPHE) D. FIELD, OF NEW YORK, N. Y., ASSIGNOR TO THE COMMERCIAL TELEGRAM COMPANY, OF SAME PLACE.

PRlNTlNG-TELEGRAPH.

EWEQZFICATION forming part of Letters Patent No. 338,343, dated March 23, 1886.

Application filed November 12, 1885. Serial No. 182,511.

To all whom it may concern:

Be it known that I, STEPHEN D. FIELD, of New York city, in the county and State of New York, have invented a certain new and useful Improvement in Printing-Telegraphs,

of which the following is a specification.

In operating printing-telegraphs it is desirable to have a high electro-motive force, and at the same time to reduce the resistance to the minimum. These conditions are attained by the employment of dynamo-electric machines for supplying current to the line. The sparking at the transmitter breakingpoints has, however, been an obstacle hereto 1 5 fore but partially and imperfectly overcome. The usual means employed has been a shunt around the transmitter breaking-points and the dynamo, this shunt including a condenser, the discharge of condenser opposing the dynamo-current when circuit is opened, and pre venting the dynamo-current from following up the points and producing a destructive spark. With this arrangement, however, the breaking-points are liable to become fused.

This I have ascertained is due to the large current that passes through the condensershunt at the instant of closing circuit A condenser having a very low resistance at the instant of closing circuit, the high electro- 0 motive force of dynamo causes a considerable current to momentarily traverse the condensershunt, and this results in fusing the breakingpoints. This difficultyI overcome by including in circuit with the condenser and dynamo- 3 5 electric machine an electromagnetic currentretarder. This is an electro-magnet preferably of low resistance, (two or three 0hms,) but having a suilicient body of metal in its core to give it the desired large inductive capacity.

0 The magnet has an action reverse to that of the condenser. Vhen the circuit is first closed, it sets up a counter electro motive force, which momentarily retards the flow of current through the shunt. This gives the condenser 5 time to become charged when it has a very high resistance and the danger of fusing the breaking-points is past. The location of the electro-magnet must be in the circuit of both the dynamo and condenser when the line is closed at the breakingpoints. To obviate increasing the liner-resistance, I prefer to put (N0 model.)

the magnet in the shunt; but it may be located in the line.

In the accompanying drawings, forming a part hereof, Figure l is an illustration, principally in diagram,of my invention with magnetic current-retarder in shunt; and Fig. 2, a similar view with magnetic current-retarder in the line.

The line L, grounded at its ends, includes the magnets M of a number of receiving-instruments. The breaking-points of the transmitter are illustrated in principle by the circuit-controlling key K.

D is the dynamo-electric machine, located in the line and supplying current thereto. The key and dynamo are shunted by a circuit,

1 2,including the condenser C. This shunt also includes the electro-magnetic current-retarder It, Fig. 1, or this may be in the line, Fig. 2, its location in either case being in the circuit of both the dynamo and the condenser when the line is closed at the breaking-points.

The electromagnetic current-retarder may be made adjustable in any of the well-known ways for adjusting induction apparatus, as by short-circuiting more or less coils at plugs a.

What I claim is- 1. The combination, with a telegraph-line,

a source of electrical energy, and a circuitcontroller, of a spark-arresting shunt around the circuit-controller and the source of electrical energy, a condenser in said shunt, and

an electromagnetic current-retarder in circuit both with the source of electrical energy and 8 5 the condenser, substantially as set forth.

2. The combination, with a telegraph-line,

a dynamo-electric machine supplying current thereto, and a circuit-controller, of a sparkarrcsting shunt around the circuit-controller 0 and said dynamoelectric machine, a condenser in said shunt, and an electromagnetic current-retarder in circuit both with the dynamo and the condenser, substantially as set forth.

3. The combination, with a telegraph-line,

a source of electrical energy, and a circuitcontroller, of a spark-arresting shunt around the circuit-controller and the source of electrical energy, a condenser in said shunt, and an electromagnetic current-retarder, also located in said shunt, substantially as set forth.

4. The combination, with a printing-tele- This specification signed and witnessed this graph line, the receiving electro-magnets, the 5th day of November, 1885. transmitting circuit-controller, and the dyname-electric machine, of-a spark-arresting STEPHEN D. FIELD. 5 shunt around the transmitting circuit-controller and dynamo, said shunt including a Witnesses: condenser and an electromagnetic current- E. L. REID, retarder, substantially as set forth. B. A. HOOPER. 

